There is increasing concern that exposure to ultraviolet light, found in solar radiation, may be involved in the etiology of ocular disorders such as age-related macular degeneration. There is, however, an incomplete understanding of the mechanisms by which light stress leads to retinal pathology. The proposed research will investigate the role of near- ultraviolet light in causing retinal degeneration and aging. Recent findings in our laboratory have established pigmented rats as a suitable experimental animal for studying near-ultraviolet light toxicity of the retina. Using primarily the rat model and in some cases rabbits, experiments are specifically designed to 2) characterize near-ultraviolet light retinal damage in sub-primate mammals and distinguish it from the well-known form of retinal damage in these species that is caused by green light (i.e. rhodopsin-mediated damage); 2) evaluate the role of various endogenous chromophores in mediating or influencing near-ultraviolet retinal damage; 3) examine the possible involvement of lipid peroxidation in the biochemical etiology of near-UV retinal toxicity; 4) examine the influence of near-ultraviolet light stress on retinal aging; and 5) evaluate the relative contribution of different visible wavelength bands in causing retinal lesions produced by operating microscope light. A quantitative, multidisciplinary approach will be applied to these studies using electroretinographic, morphometric and various biochemical techniques. The intention of the proposed studies is to provide an in-depth analysis of the mechanisms by which near-ultraviolet light leads to retinal pathology. The information obtained from these studies could help to predict the conditions predisposing the retinal to near-ultraviolet damage and to devise strategies for preventing and managing photically-induced retinal disease.